Patent GB-206042-A (GB)
Title: Improvements in and relating to automatic reclosing electric circuit-breaker systems
IPC: H02H3/06
Filed: 1922-12-21
Abstract: 206,042. British Thomson - Houston Co., Ltd., (General Electric Co.). Dec. 21, 1922. Cut-out arrangements.-In an automatically-reclosing circuitbreaker system employing a current-limiting impedance the voltage across which is utilized for the reclosing circuit, a polarized relay which need not be disconnected from the loud circuit before the circuitbreaker recloses is employed to control the reclosing circuit. In the arrangement shown in Fig. 1, the circuit-breaker 1. which has a resistor 8 connected across it, is closed and maintained closed by the winding 7 controlled by the contacts 11, 11<1> ot the relay 12. The relay has a polarizing winding 22 of high resistance connected across the load 2, 3 through the contacts of the overload relay 10. The movable armature 23 is energized by a fixed operating winding 17 connected directly across the load circuit. The windings develop polarities in the armature and in the fixed field structure such that, in the reclosing position shown, the armature is held in attraction to the poles, against the action of the spring 20. In case of overload or short circuit the relay 9 operates, thereby breaking the closing circuit through the lead 30 and the overload relay contacts, and at the same time breaking the polarizing circuit and causing the opening of the relay 12. The circuitbreaker 1 opens and the resistor 8 is inserted in the load circuit. The overload relay recloses after an interval and, when the load resistance increases sufficiently, the voltage across the load impressed on the operating winding 17 becomes adequate to close the relay, which completes the reclosing circuit. The full load potential impressed on the winding 17 merely acts to close the contacts 11, 11' more firmly. In the arrangement shown in Fig..2 employing a different form of polarized relay, the polarizing coil 22 is connected in series with the resistor 8 instead of directly across the supply 4, 5. The operating winding on the central limb produces a flux which aids that on the right-hand limb and reduces that on the left-hand limb. In consequence, when the load resistance is adequate, the relay closes against the action of the spring 45. In order to compensate for temperature variations in the polarizing winding, which usually has a positive temperature coefficient, resistances of negative temperature coefficient may be connected in series therewith or a resistance of higher positive temperature. coefficient may be connected in parallel therewith. The two methods may be combined. In the arrangement shown in Fig. 4, a maximum current is allowed to flow into the load circuit, on fault, before the circuit-breaker 1 opens. An additional circuit-breaker 60, shortcircuited by the resistor 62 and closed by the coil 63, is connected in series with the first and is controlled by the overload relay 10. The opening of circuit-breaker 1 is controlled by a thermostat 61 mounted upon the resistor 62. The closing coil 63 is connected to the supply 4, 5 through the contacts of 1 and 9 and the closing coil 7 is connected to 4, 5 through 61 and the ccntacts 11, 11<1>. On overload, 9 opens, breaking the circuit of coil 63 so that 60 opens, inserting 62 which leaves a load on the supply in excess of the normal. Resistor 62 heats up, 61 opens and, in consequence, 1 opens inserting resistor 8. The de-energization of winding 22 causes 11, 11<1> to open and when, after an interval, 9 recloses, 63 is re-energized but not sufficiently to cause operation. When 62 cools down. 61 recloses and 22 is energized and, when the load resistance is high enough, the voltage across 17 is adequate to reclose the relay contacts 11, 11<1> whereupon 1 recloses and then 60 recloses.